Abstract: The system includes a distance protective relay for power lines which includes a logic capability which is responsive to settings entered into the relay by an end user to implement the value of those settings into stored thermal model equations which emulate the temperature of the power line conductor. The logic within the relay is organized and has the capability of receiving the setting values entered by the user and to use those in the logic equations to determine the temperature of the conductor.

Abstract: A system used in a protective relay for motors for transitioning the value of the trip threshold to a motor start (stall) condition. The calculated transition trip threshold value follows I2t, specifically, the current to the motor. The transition trip threshold value includes a small fixed initial (offset) value, so that the increase in the trip threshold during transition to the actual start condition threshold value is always slightly ahead of the increase in the I2t value, preventing a trip until the input current exceeds the final trip threshold for the start condition.

Abstract: The current differential relay operates without adjustable settings, and includes a phase current differential element with a predetermined threshold, responsive to local phase current values and remote phase current values, to detect three-phase faults and producing a first output signal if the threshold value is exceeded. Either a negative sequence current differential element or two phase current differential elements, also having predetermined threshold values and responsive to the local and remote phase currents, detect phase-to-phase faults and phase-to-phase-to-ground faults and produces a second output signal if the predetermined threshold is exceeded. A negative sequence or zero sequence current differential current element, with a predetermined threshold value is responsive to the local and remote phase currents to detect phase-to-ground faults and to produce a third output signal if the threshold is exceeded.

Abstract: A digital protective relay for power systems includes a memory location for storing information entered by an operator concerning the operation of the relay. Conventional reports of the relay will include a reference to such operator-entered information. This information will include particular actions taken by the operator relative to the relay, as well as notes made by the operator on particular actions and/or entry of and changes to the relay settings. The entered information can be conveniently retrieved by the operator.

Abstract: The system tests front panel lights, such as LEDs, on an electronic instrument, the front panel lights being normally used to indicate the status of selected output conditions of the instrument. The system also uses the LEDs to communicate additional information concerning the instrument, in particular the operation of the clock system for the instrument. The system includes a plurality of timers, each timer being associated with one front panel LED. The user sets the timers a specific amount of time (e.g. one second) apart, with each LED being programmed with a different timer. The LEDs light in succession in response to the clock reaching a preselected time. If one or more of the LEDs do not light, failure of the LEDs is indicated. If the LEDs do not light in proper order or at the expected time, investigation of the clock system is indicated.

Abstract: The relay system obtains voltage and current values from a power line and uses a first sampling element to sample the voltage and current values at selected intervals of time. The resulting sampled signals are used for power system-wide protection, control, monitoring and metering. The sampled signals are then resampled at a rate which is a selected multiple of the power system frequency. The results of the resampling are used by processing circuitry for protection functions including fault determinations.

Abstract: The system includes a plurality of protection application elements to accomplish various power system protection functions, including for example line protection, line fault location, current direction determination, breaker protection and synchronism check, among others. The system includes local sources of current and voltage information for the protective functions as well as a receiving section for receiving such current and voltage values from a remote source, such as another protection device, as well as other necessary input information for the protective functions. A selection logic section is responsive to the output of the protective function elements, as well as the local and remote data to determine whether the primary or local sources are to be used. The outputs of the protective function elements are used by an output section to control circuit breakers and the like and are also transmitted, with the local and remote source quantities, to other protective devices.

Abstract: The relay obtains three-phase current signals from two power line sources thereof, typically two independent feeder lines. The two sets of signals are processed by a single processing means, which independently controls the circuit breakers associated with each feeder line, depending on the values of current obtained.

Abstract: The system for determining protection quality of a protective relay and related functions of the protection system include obtaining information concerning the output status of the various protective elements in the relay. The status of various operations in the protective element are also evaluated against specific standards. The operation of supervisory and control elements affecting the action protective elements are also evaluated. Other aspects of the relay, including the availability of the relay and the operation of the voltage and current transformers are also evaluated. In addition, associated aspects such as the status of the communication channels, the station voltage availability and the condition of the trip and close circuits are monitored. All of the above is analyzed in a summary report to provide an indication of protection quality for the relay and associated protection system functions.

Abstract: A visual monitoring system for an electric power substation includes at least one camera for obtaining the image of various operational indicators in the substation, either within the control house, outdoors or both. The indicators could be the status of various gauges, including current, voltage and temperature gauges, or other structural elements, such as the position of various switches, the level of oil in a transformer sight glass, or whether a transformer fan is running, among others. The image is then enhanced to accentuate the desired features, and the desired data is then image detected. The resulting information is then compared against a standard to determine whether or not the operational status of the indicator is abnormal.

Abstract: A microprocessor-based multifunction overcurrent relay for protecting power systems has a plurality of overcurrent elements implemented in a software program. Sufficient overcurrent elements are provided to accomplish a selected one of three independent applications, including feeder protection, motor protection, or breaker failure protection. The relay includes elements for selecting one application by the user from the three possible applications and produces output signals when an overcurrent condition is determined.

Abstract: The communication system includes transmitting output status bits indicative of a function of the relay directly from one microprocessor-based protective relay in a power system to a second companion microprocessor-based relay. Each relay has transmit and receive modules connected by a communications link, with the transmit and receive modules using the logic output and input bits produced by the respective relays in their respective relay calculations.

Abstract: The communications processor includes an electronic network system which includes a total of 17 individual ports, four quad universal asynchronous receiver/transmitter devices, each of which serves four separate ports, and a microprocessor which processes and controls the flow of data under the control of stored control programs, command settings and command logic. Connected to a plurality of those ports referred to as IED ports are intelligent electronic devices IEDS, such as protective relays or meters, while connected to other ports, referred to as master ports, are remote terminal units or a local computer or terminal or a modem which can be connected to an external telephone line. The apparatus includes both buffer and long-term storage for development of a database, as well as an IRIG-B capability for synchronization of the time clocks of the connected devices.

Abstract: Voltage comparisons are made for each of the phase-phase voltages on a low side of a distribution transformer in a power system against a threshold, approximately 0.7 nominal secondary voltage, which is less than the value of at least one phase-phase voltage when only one high side fuse has operated. High outputs result when the phase-phase voltages exceed the threshold. At the same time voltage comparisons are made of each of the phase-phase low side voltages and a second threshold, approximately 0.2 nominal secondary voltage, which is substantially less than the first threshold. High outputs result when the voltages are below the threshold. A circuit output is provided which can be used to trip a low side circuit breaker when at least one output of the first comparisons is high and at least one output of the second comparisons is high.

Abstract: The angle between the negative sequence and zero sequence currents for a power signal on a transmission line is measured and compared against a plurality of successive angle ranges from 0.degree. to 360.degree.. If the angle is 0.degree..+-.30.degree., an AG fault is indicated and a first section output is produced blocking ground elements BG and CG and phase-to-phase elements AB and CA. An angle of 120.degree..+-.30.degree. indicates a BG fault, resulting in a second output blocking ground elements AG and CG and phase-to-phase elements AB and BC, while a phase angle of 240.degree..+-.30.degree. indicates a CG fault, resulting in a third output blocking ground elements AG and BG and phase-to-phase elements BC and CA.

Abstract: The relay includes an input module capable of receiving 70 volt and 5 amp signals, respectively, from conventional instrument transformers, which are responsive to power line signals at their primaries. Output signals from the input module have specified, standardized levels suitable for electronic processing circuits, i.e. 1.4 volts and 0.1 volt. The output signals from the input module are applied through an accessible connector to a separate processing module which uses those signals in a conventional manner to determine possible faults on the power line. Low-level testing is accomplished by testing the outputs of the input module and by applying test signals simulating the standardized outputs of the input module to the processing module.

Abstract: The system includes a blocking counter which is set to 255 quarter cycles and the output contacts of the protective relay are blocked for five quarter cycles if the first order difference between two successive quarter-cycle samples of current is above a selected threshold, referred to as the last previous and the first samples. The first order difference between the first and the next successive (second) samples is compared against a second threshold and the instantaneous value of the current sample is compared against the second threshold. If both comparisons are above the second threshold, then the output contacts are unblocked. If not, such that a constant DC A/D converter output or an A/D spike is indicated, then the outputs remain blocked for the full five quarter cycles, which is sufficient time to permit the A/D spike to disappear and to recognize a constant DC output from the A/D converter.

Abstract: The motor relay includes thermal models representing the start and run conditions of a motor. The thermal models are implemented using measured current values and certain known operating parameters available from the manufacturer, specifically full load current, locked rotor thermal time and rated service factor. The thermal model information is compared with threshold thermal model values to determine when an overload condition has been reached.

Abstract: Voltage and current on a power transmission line are first obtained, filtered and converted to digital representations. The positive sequence components of the voltage and current are determined and the impedance at the relay is then calculated from those positive sequence voltages and currents. The positive sequence impedance is converted into a magnitude and phase angle representation and then compared against a load pattern which is also represented by magnitude and phase angle representations. If the calculated impedance at the relay is within the load impedance pattern, the distance relay is prevented, i.e. blocked, from sending an output signal to trip a circuit breaker protecting the transmission line.

Abstract: A directional element measures the negative sequence voltage and the negative sequence current and from those quantities produces a scalar quantity related to the negative sequence impedance of a power transmission line relative to the location of the directional element. The magnitude of the negative sequence impedance is calculated from the magnitude of the negative sequence voltage and magnitude of the negative sequence current. The scalar quantity is then compared against two threshold quantity settings, one to determine a forward fault and the other to determine a reverse fault. The threshold quantity settings include, respectively, a selected fraction of preselected basic threshold values and a selected fraction of the magnitude of the negative sequence impedance. The scalar quantity must be less than the forward threshold quantity for a forward fault and greater than the reverse threshold quantity for a reverse fault.